1. Field
The present invention generally relates to key levelers used to level the keys on the keyboards of musical instruments, and more particularly to such key levelers used in the initial assembly, repair, and restoration, and rebuilding of pianos or other piano-like keyboards to aid in leveling the keys.
2. State of the Art
Referring to FIG. 1, therein is shown a keyed musical instrument in the form of a conventional upright piano 20 that includes a cabinet 23 supported by a plurality of downwardly dependent legs 26 on a ground surface 29, a music stand 32, and a plurality of pedals 35 supported just above the ground surface 29 by a downwardly dependent pedal support 38. A keyboard structure 41 is enclosed by the cabinet 23 and accessible through a hinged door 44 for servicing. A keyboard cover 47 is hinged to the cabinet 23 to cover the keyboard structure 41 during periods of non-use.
Referring to FIG. 2, the keyboard structure 41 includes a keyboard 50 containing a standard number of white keys 53 and black keys 54, an action 55 that includes a hammer assembly 56 and an action mechanism 59 for rotating the hammer assembly 56, and a plurality of strings 62 retained in a vertical orientation under tension by a string support structure 65 affixed to the cabinet 23.
The keyboard 50 includes the keys 53 and 54 supported on a back rail 68, a balance rail 71, and a front rail 74 mounted to a key bed 77 all of which extend a width “KW” of the keyboard 50. A key stop 78 extends upwardly from the key bed 77. The keys 53 and 54 are each supported by a balance rail pin 80 attached to the balance rail 71 with a flexible balance rail washer 83 so as to freely pivot thereon. A thickness “TBW” of the balance rail washers 83 determines how high each key 53 and 54 is while in an non-depressed, rest position.
Referring specifically to the white keys 53 (the black keys 54 are similarly constructed and supported), they include respective front ends 84 with top panels 86 affixed thereto each having a top surface 87, and a face panel 88 affixed thereto. The front ends 84 of the white keys 53 are laterally retained by respective front rail pins 89 that extend upwardly from the front rail 74 into respective slots 92 of the white keys 53. Respective flexible front rail washers 95 slip over the front rail pins 89 under the front ends 84 of the white keys 53. A thickness “TFW” of the front rail washers 95 determines how far the front end 84 of each white key 53 may be depressed to a depressed position while playing. The white keys 53 each include a rear end 98 with an upwardly dependent capstan screw 101. The rear end 98 engages a flexible back rail cloth 104 affixed to the back rail 68 when the white key 53 is in the rest position. As the front end 84 of each white key 53 is depressed, it rotates about the balance rail 71 with balance rail washer 83 such that the front end 84 contacts the front rail washer 95.
The action mechanism 59 includes a plurality of action brackets (not shown) disposed along a main action rail 110 affixed to the cabinet 23 extending along the width “KW” of the keyboard 50. A plurality of action mechanisms 113 are disposed between the action brackets. The action mechanisms 113 include respective whippen flanges 116 that are connected to the main action rail 110 that correspond to respective of the white keys 53. Respective whippens 119 are rotatably supported by the whippen flanges 116 using respective pivot pins 122. Sticker cloths 125 are affixed to stickers 128 that are rotatably connected to the whippens 119 using respective pivot pins 129 extend downwardly from the whippens 119 to contact the capstan screws 101. Respective jack flanges 130 are affixed to the whippens 119 that rotatably support respective small and large jack portions 131 and 132 of respective L-shaped jacks 134 using pivot pins 137. Respective jack springs 140 are arranged on the whippens 119 that bias the jacks 134 in a counterclockwise rotational direction. Respective back checks 143 are interconnected with respective bridle wires 146 disposed in front of the whippens 119 to elastically receive respective catchers 149 when moved upon depression of respective of the white keys 53. Pairs of the bridle wires 146 and the catchers 149 are interconnected using a bridle strap 152 so as to lock restoration movements of the hammer assembly 56 with the whippens 119. As the whippens 119 are rotated upwardly, the large jack portions 132 of the jacks 134 come into contact the small jack portions 131.
Respective hammer butts 173 are rotatably supported by respective butt flanges 176 connected to the main action rail 110 using respective center pins 179. The hammer assemblies 56 are connected to the hammer butts 173. The catchers 149 are attached to the hammer butts 173 using respective catcher shanks 185. The hammer butts 173 are biased in a counterclockwise rotational direction using respective hammer butt springs 188. The hammer assemblies 56 contact respective hammer butt pads 191 affixed to hammer rails 194.
The hammer assembly 56 includes a hammer shank 200 and a hammer 203 connected to a tip end 204 of the hammer shank 200. The hammers 203 that correspond to the keys 53 and 54 gradually increase in weight in from higher pitched to lower pitched keys 53 and 54.
In the upright piano 20, three of the strings 62 are arranged for each of the keys 53 and 54 belonging to each of a high-pitch register and a middle-pitch register. One or two strings 62 are arranged for each of the keys 53 and 54 belonging to a low pitch register. The strings 62 are gradually increased in thickness from higher pitch to lower pitch strings 62 so that frequencies are gradually reduced. Likewise, the strings 62 increase in length in a pitch-descending order from higher pitches to lower pitches.
When a piano player depresses one of the white keys 53, the capstan screw 101 that extends from the rear end 98 thereof moves upwardly to rotate the corresponding whippen 119 in the counterclockwise direction. The large jack portion 132 of the jack 134 pushes up the hammer butt 173 to rotate the hammer assembly 56 in the clockwise direction such that the hammer 203 contacts the strings 62. After striking the strings 62, the hammer assembly 56 rebounds and rotates in the clockwise direction. The catcher 149 connected to the hammer butt 173 through the catcher shank 185 moves rightwards and contacts the back check 143 to temporarily stop the hammer assembly 56. The jack 134 then moves downwardly and is interlocked with the restoration movement of the whippen 119 which moves downwardly, being interlocked with the restoration movement of the white key 53. The large jack portion 132 moves below the hammer butt 173 ready for a next key depression.
Manufacturing variations in all parts of the keyboard 50, repeated use, humidity, and other factors require that the balance and front rail washers 83 and 95 be of varying thicknesses “TBW” and “TFW”, or that shims 205 made of cardboard, paper, or other suitable shimming materials be used to define the rest and depressed positions of each key 53 and 54. The individual rest and depressed positions of the keys 53 and 54 affect the feel of the keyboard 50 to piano players and the sound produced by the piano 20. Therefore, it is important that the top surfaces 87 of each white key 53 are in a common rest plane “WRP” when in the rest position and in a common depressed plane “WDP” when depressed. Likewise, it is important that top surfaces 207 of each black key 54 be in a common rest plane “BRP” when in the rest position and in a common depressed plane “BDP” when depressed.
The process of a piano technician assuring that the top surfaces 87 of the white keys 53 are in the same rest and depressed planes “WRP” and “WDP”, and the top surfaces 207 of the black keys 54 are in the same rest and depressed planes “BRP” and “BDP” is known as leveling the keys 53 and 54. The process of leveling the keys 53 and 54 refers to adjusting the thickness of the balance and front rail washers 83 and 95, and the shims 205 under the keys 53 and 54.
Referring to FIGS. 1, 2, and 10, a conventional leveling process is conducted as follows. The white keys 53 are leveled first. Two outermost white keys 53a and 53b respectively disposed on extreme left and right ends 208 and 209 of the keyboard 50 are fixed in a position and not allowed to be depressed using retaining washers (not shown) placed on the front rail pins 89. An adjustment bar (not shown) is placed on top of the white keys 53a and 53b spanning over a remainder of the white keys 53. A bottom surface of the adjustment bar is planar or may bow slightly upwardly in a middle portion of the adjustment bar. Bowing is desirable since the keys 53 and 54 in a middle portion 210 of the keyboard 50 produce the most commonly used musical notes. Thus, they are used more often causing their balance and front rail washers 83 and 95 to wear more quickly. The bow compensates for this wear at the time of leveling the keys 53 and 54 so less frequent key leveling is required.
Once the adjustment bar is placed onto the white keys 53a and 53b, the technician manually measures or “eyeballs” how far the top surface 87 of each white key 53 is above or below the bottom surface of the adjustment bar. The white keys 53 that require leveling are individually removed from the key bed 77. The technician judges what amount of shimming is needed to be added or removed and whether additional balance rail washers 83 and/or shims 205 of specific thicknesses are needed to bring the top surface 87 of the white key 53 to the rest plane “WRP”. The balance rail washer 83 may need to be removed from the balance rail pin 80. Removal of the balance rail washer 83 is complicated by lack of visibility and its small size. A special tool (not shown) is needed to aid in its removal. The technician may likewise place additional balance rail washers 83 and shims 205 onto the balance rail pin 80. The technician then returns the white key 53 to the key bed 77. The adjustment bar is again placed across the white keys 53a and 53b and the process is repeated for that white key 53 to verify that it is properly leveled. If not, the process is repeated for that white key 53 until the proper rest position is achieved. The process is repeated for each white key 53.
When all of the white keys 53 are leveled with respect to the rest plane “WRP”, leveling them with respect to the depressed plane “WDP” begins. A dip tool (not shown) is used for the technician to gauge the depth each white key 53 travels downwardly from the rest position to the depressed position in which the front end 84 contacts the front rail washer 95 on the front rail pin 89. The white keys 53 that require leveling are individually removed from the key bed 77 and the front rail washer 95 is removed from the front rail pin 89. The technician judges what amount of shimming is needed to be added or removed and whether an additional front rail washers 95 and/or shims 205 of specific thicknesses are needed to bring the top surface 87 of the white key 53 to the depressed plane “WDP”. The technician places the required additional front rail washers 95 and shims 205 onto the front rail pin 89 and returns the white key 53 to the key bed 77. The adjustment bar is then placed across the white keys 53a and 53b and the process is repeated for that white key 53 to verify that it is properly leveled. If not, the process is repeated for that white key 53 until the proper depressed position is achieved. The process is repeated for each white key 53.
When all of the white keys 53 are leveled with respect to the rest and depressed planes “WRP” and “WDP”, the black keys 54 are leveled. Once again, the black keys 54 are first leveled with respect to the rest plane “BRP”. The adjustment bar is used, but the top surfaces 207 of the black keys 54 typically are about one-half inch higher than the top surfaces 87 of the white keys 53. Therefore, a tool (not shown) is used that straddles the white keys 53a and 53b for the technician to gauge whether or not the top surfaces 207 of the black keys 54 are in the rest plane “BRP”. The black keys 54 that require leveling are individually removed from the key bed 77 and adjusted as explained for the white keys 53.
When all of the black keys 54 are leveled with respect to the rest plane “BRP”, leveling them with respect to the depressed plane “BDP” begins. The dip tool is used for the technician to gauge the depth each black key 54 travels downwardly from the rest position to the depressed position. The black keys 54 that require leveling are individually removed from the key bed 77 and adjusted as explained for the white keys 53. Once all of the black keys 54 have been leveled, the white keys 53a and 53b are freed up by removing the retaining washers.
The adjustment bar and process for leveling the keys 53 and 54 has several serious shortcomings. Firstly, it is very tedious and time consuming with the ultimate result depending on the technician's skill level and patience. The process requires repeatedly: 1) placing the adjustment bar across the keys 53 and 54; 2) estimating the error; 3) estimating the proper balance rail washers 83, front rail washer 95, and shims 205; 4) removal of the keys 53 or 54; 5) making the appropriate adjustments; and 6) reattaching the key 53 or 54 for rechecking. The process is repeated as needed for each key 53 and key 54 before moving to the next.
Secondly, the process is prone to inaccuracy due to the fact that the technician needs to estimate washer and shim requirements. This is an angular relationship in the case of the balance rail 71 and the balance rail washer 83 relative to the top surfaces 87 and 207 of the white and black keys 53 and 54. Thus, the initial shimming estimate requires further mathematical manipulation by the technician to compensate for this.
Thirdly, the process is prone to over-adjustment by the technician. If the white keys 53a and 53b are already set too high or too low at the beginning of the process, all of the keys 53 and 54 will be adjusted according to them resulting in unnecessary over-adjustment. Such over-adjusting can result in problems with operation of the keys 53 and 54. At times, this requires the technician to horizontally reposition and re-level one or more problem keys 53 and 54.
There is a need for a key leveler and method of use that solves the problems encountered using the adjustment bar and process for leveling the keys by: 1) being easy and quick to use; 2) having consistent results that are not so dependent on the technician's skill level and patience; 3) not being an iterative process in which adjustments to one key affect other keys which must be redone; 4) being accurate by telling the technician exactly what the washer and shim requirements are and without requiring any calculations; and 5) not being prone to over-adjustment of the keys by the technician.